[snow crunching] It takes a special person to live here long enough to witness the creeping baselines of change.

[device beeping] [interviewer] Is that your phone that beeped?

I turned my phone off, not that I ever get many calls, but... [Shane] There's not a lot of reception up in the Rocky Mountains, where we met billy barr.

[billy] This'll be my 50th winter out here.

[Shane] He's been out here for a while then.

[billy] Yeah, I got here in '72.

[Shane] And there aren't a whole lot of people up here.

[billy] I'm here all by myself, just talking to myself.

"How you doing?"

"Fine."

"How you doing?"

"Ah, I'm not doing so good."

See, I do that every day.

[Shane] I mean, sometimes you've just got to check in with yourself.

But 50 winters all alone is not why billy has achieved oracle status.

That comes from a very particular skill.

You see, billy's not a scientist.

He is an accountant.

High in the Rocky Mountains, billy started accounting for... snow.

[billy] So I started writing it down just because I had the time.

I've always kept track of numbers, so--I mean, I'm an accountant.

[Shane] At his homemade weather station, he recorded what he found.

[billy] And as I did that year after year, it started to become more and more interesting... especially looking at long-term trends.

This was in, uh, late April 1974.

[Shane] And he started charting everything.

[birds chirping] [billy] And so if you look over here, it shows that it snowed 26 inches overnight.

[Shane] As with all bookkeeping enthusiasts, he got a bit carried away with the details.

Cloud cover, wind strength, temperature.

Daily snowfall, depth of snow, the water content and weight of that snow... and so it went on.

Nothing went unobserved.

[billy] I had this great graph once that showed the amount of snow in the winter as compared to my chocolate consumption.

[Shane] While billy satisfied his sweet tooth, the ledgers mounted up.

A 50-year record of exactly how the snow and nature interact on a day-by-day basis.

Amazingly, it wasn't until the 1990s that scientists got ahold of billy's records.

Only then did they realize these data were showing a creeping change.

[billy] These are the birds I saw each day.

Uh, the first tree swallow, the first yellow-bellied sapsucker.

They're not even called that anymore.

The first butterfly.

And here is the first hummingbird and the first glacier lily on that same day.

[Shane] One key flower that billy tracks is the glacier lily.

The glacier lilies are the first flowers to emerge when the snow melts in the spring.

[billy] This area here is where there's a glacier lily population, and since I go by this every day, I used that as the indicator of when they first start to flower.

[Shane] He told us we should come back.

[billy] If you come out in spring, you'll get to see it.

[Shane] So we did.

[birds chirping] [water flowing] [insects buzzing] The importance of billy's records was really brought home by the timing of this flower and its intimate connection with an animal, one that has undertaken a gargantuan cross-continental migration.

Traveling over 1,500 miles to get here from Mexico... ♪ on wings beating 50 times a second... the broad-tailed hummingbird lives life in the fast lane, and this little dude is absolutely desperate for food.

[chirping] The glacier lily is perfectly timed for his arrival, providing a crucial source of nectar... but billy's data shows a clear mismatch between flower and bird... and the connections are getting more and more out of sync each year.

The flowers now bloom nearly 3 weeks earlier.

[billy] So the glacier lilies are past prime flower when the hummingbirds get here.

[Shane] Some have wilted before the birds even arrive.

billy's data showed that in just 20 years from now the hummingbirds will miss the flowers entirely.

They come to these mountains to breed.

Without the flowers, this will be impossible.

♪ Take it from me.

You can only see long-term shifts like these with the kind of dedicated work billy's put in, but we wondered how much longer would billy stay here?

[billy] I honestly don't know how many more years I'll be out here.

I'm hoping for 10 more, but, you know, it's cold and it's windy.

It's difficult.

[Shane] billy's detailed data reveals a microcosm in flux, showing intricately evolved rhythms of life.

His recordings are now considered to be some of the most significant long-term data on climate change ever collected.

♪